Water jet discotomy using the microinvasive approach - In vitro-testing and the first clinical aspects of a new procedure.

Aim: The difference in consistence of the nucleus pulposus and the annulus fibrosus allows the water jet to selectively remove the nucleus in a closed vertebral disc at a certain pressure range. The aim of the study was to in vestigate the use of water jet cutting in microinvasive spinal surgery. Met hods: A comparison in terms of efficiency between the water jet and those o f the laser and APLD (automatic percutaneous lumbar discotomy) was achieved by plastic reconstruction of the resected spaces using the in-vitro-model of the spinal column of young pigs. The in-vitro-study was followed by a pr ospective clinical study with 21 patients. Results: The in-vitro-employment of the three different methods showed that there were no; significant diff erences in volume of the removed nucleus material. During the use of the hy dro jet at 50 bar and simultaneous suction the intradiscal pressure measure d in vitro remained below 1 bar. Clinical tests on the 21 patients showed g ood to very good results in 71 % of the patients tested (mean follow-up 5.8 months). No complications were found. As working mechanism the pure mechan ical effect and the influence on chemical processes within the nucleus rema in points for discussion. Conclusion: The current studies results demonstra te that hydrojet spinal surgery might be a safe new method for surgery of d isc protrusion and contained prolapse.